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I'm just getting started with bitcoin and haven't acquired any significant amount yet, but want to feel relatively secure before I do. And at the moment, my fear of losing bitcoins or a device on which I store bitcoins is slightly greater than my fear of having them stolen so I'm investigating how to make a paper backup. I have looked around and what I have seen seems more complicated than necessary. I am wondering if I could simply:

  1. Start up my bitcoin 0.7.1-beta client
  2. Transfer all my bitcoins to some address in the client
  3. Open the debug window console
  4. Enter walletpassphrase <my passphrase> 60
  5. Enter dumpprivkey <my address with all the bitcoins>
  6. Print the private key that is displayed

Then if I ever need to recover it, I could import that private key into any other bitcoin client. If it's the same bitcoin client newly installed, I could enter importprivkey <my key>.

My one concern about this is that I have somewhere read that some bitcoin wallets "un-steal themselves" and I am worried and wondering if that means that coins may be automatically transferred to another address at some point, at which time my paper backup would become useless.

How wise is this plan? Is there another way I can or should generate a private key and address to which I can send bitcoins without actually having the private key stored on my system if I have a concern about the security of the system?

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3 Answers 3

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I recommend to check out “bitaddress.org”.

You can grab the whole page (all the java-script it needs is in it) via GitHub and run the brain wallet tab offline.

Type in a damn good pass-phrase and record it. The pass-phrase. Send your bitcoins to the public key that results and re-create the private key with the same pass phrase when you want them.

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    This is a very interesting and cool page. Still trying to figure out why I want bitcoins more -- because they're a good investment or because the technologies and ideas just seem so cool to me! :) I probably won't use a brain wallet, just a "Single Wallet" -- then I don't have to rely on my fallible memory, and if I should become incapacitated, someone else can make use of my savings.
    – BlueMonkMN
    Commented Dec 6, 2012 at 20:21
  • Probably the most secure thing to do every time I spend anything would be to generate a new "Single Wallet" address and transfer everything I want to keep into that, and then import the private key of the remainder wherever I want to spend it, eh?
    – BlueMonkMN
    Commented Dec 6, 2012 at 20:34
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I've been under the impression that a paper wallet backup is best for something like a savings account or cold storage. It's impractical to print off the several keypairs that the client generates on initialization (for some clients) or remembering to print out a keypair every time you create a new address, something you should be doing anew for each serious transaction.

Backing up to USB or a NAS or something regularly is the best way to guard against temporary failures. Printing is the best way to keep a balance completely off the network.

If you really want to pursue printing keypairs periodically, you could use something like optar to create a paper wallet that's really just a printed version of wallet.dat. That's more practical and more able to be automated, but still a hassle.

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  • My concern with USB is that I am trying to think of the best way to store coins in a "savings" or "cold storage" account/address, and I know that electronic devices can go bad over time. I want to be sure that if I "forget" about the account for a decade or two, when I come back to it, there won't be any corruption or data loss or compatibility problems preventing me from accessing the account. This isn't something I want to do periodically. I want to be able to send coins to the address and potentially forget it for years at a time.
    – BlueMonkMN
    Commented Dec 6, 2012 at 16:46
  • I don't understand the need to worry about multiple addresses and periodic printing of keys. Can't I just send everything to one address and print the one private key for that address and keep it?
    – BlueMonkMN
    Commented Dec 6, 2012 at 16:57
  • If you're using a paper wallet for a single address for savings, all the talk of periodic backup is moot.
    – Colin Dean
    Commented Dec 6, 2012 at 20:02
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I believe it is feasible way to do that :-)

However, there is a catch: once you have done that, you should not use that wallet for payments. Otherwise you'll risk your funds being moved to some hidden addresses your paper wallet knows nothing about. Every payment you make from the original wallet invalidates your paper wallet. For that reason you may want to backup your wallet.dat on a USB-stick (or CDROM or both) as soon as you print out your paper wallet, for fast retrieval, if needed, and then delete wallet.dat from your hard drive. Putting wallet.dat out of use is a logically consistent step, since the very idea of paper wallet means taking your funds off-line.

You may still send funds to that address of yours, though.

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